1. Field of the Invention
The invention relates to mineral ore treatment, particularly to oxidation of sulfides in mineral ores by means of enzymes generated from microorganisms. Hydrogen sulfide is produced as a product of the reaction, a portion of which is further oxidized to sulfuric acid. Metal impurities are converted to soluble forms by the sulphuric acid and can then be removed by leaching techniques to leave a concentrate which is high in metal values, such as silver concentrate.
2. Disclosure Statement
The bacterial leaching of mineral ores is known. For example, O'Connor et al in U.S. Pat. No. 3,679,397, patented July 25, 1972, and Mayling, in U.S. Pat. No. 3,455,679, issued July 15, 1969, specifically mention certain bacterial species for carrying metals into solution, and Zaffe in U.S. Pat. No. 3,272,621, patented Sept. 13, 1966, identifies other species of microorganism for a similar purpose. U.S. Pat. No. 3,923,540, issued Dec. 2, 1975, to Usami et al, suggests action of an enzyme produced by a species of bacteria, and further discloses consumption of sulfur or other sulfur compounds by such bacteria.
In U.S. Pat. No. 3,959,436, issued May 25, 1976 to Watts, addition of aqueous hydrogen peroxide to mineral leaching solutions is disclosed, with the additional suggestion of addition of sulfuric acid solutions and elemental sulfur.
Although use of biological systems for effecting mineral leaching can be found in certain of the patents listed above, none discloses specifically the use of yeast or biological material which metabolizes sugar, molasses, starch, or malt, for the purpose of placing mineral contaminants into solution with evolution of hydrogen sulfide or the further oxidation of evolved hydrogen sulfide to sulfuric acid. Moreover, many of the patented processes disclosed produce sulfur, rather than utilize elemental sulfur which has been added to the leach mixture. Accordingly, a need exists for a simple process for removing acid soluble contaminant metals in sulfide rich ores.